Radioactive materials are at large after a truck carrying medical treatments was stolen in central Mexico on Monday.

The stolen truck held cobalt-60, which is used to treat cancer in radiation therapy, the Los Angeles Times reported.

Mexico detailed the theft to the International Atomic Energy Agency, the United Nations nuclear watchdog, which released a statement.

"At the time the truck was stolen, the [radioactive] source was properly shielded," the statement said. "However, the source could be extremely dangerous to a person if removed from the shielding, or if it was damaged."

The cobalt-60 was being taken from a hospital in the city of Tijuana to a radioactive waste storage center when the truck was stolen in the town of Tepojaco, which is near Mexico City.

Mexican officials believe the thieves were after the truck, not the radioactive material, but the theft still invites such uneasy scenarios as the cobalt-60 falling into the hands of drug and extortion gang members.

IAEA Director General Yukiya Amano identified the material last year as one that could be used along with conventional explosives to make up a "dirty bomb." The crude explosive is used to terrorize but is less likely to cause large loss of life.

"These materials, such as cobalt-60, could be used along with conventional explosives to make so-called dirty bombs. A dirty bomb detonated in a major city could cause mass panic, as well as serious economic and environmental consequences," Amano said at a nuclear security summit in South Korea.

Mexican officials are searching in six states and the capital for the truck and have cautioned people not to open the material's protective shielding.

The IAEA said earlier this year that more than 100 incidents of theft and other illegal activities involving nuclear and radioactive material are reported to the agency each year, according to Reuters.

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